Big Mike

iTrader: (4)

My friend has a 2000 SS, totally stock except for a lid and filter. Recently his car started bugging out on him. It would surge and miss like crazy at low rpm. The dealer installed a new speed sensor but that didn't solve the problem. The dealer then hooked up the Tech II Snap Shot. When they played it back, it showed his timing jumping from 15 to 41 at 1900 rpms. This is driving him crazy, and the dealer can't explain. In the quest to help my buddy out, I figured I'd post it here cause you guys know best. Any ideas?

Thanks

Ozz

Is it getting KR? if so do a search on KR here there is a ton of info.

Ozz

98blackSS

what do all the other parameters look like?

BigTex

iTrader: (16)

I have a similar problem. Under load (OD on the freeway) with part throttle increase, mine does it. The lower the rpms, the worse. I can watch it with autotap and have 0 KR and timing goes form 30s to teens, and bounces back and forth. The result is a "surge" feeling as the timing goes back and forth.

Big Mike

iTrader: (4)

Update, there is no knock retard and all other parameters are dead on. One thing I failed to mention is that when this "surge" happens, the speedometer bounces from the actual mph to zero and all in between. Now the speed sensor shows the actual mph, even when the speedometer jumps around.

Big Mike

iTrader: (4)

I'm not sure what the other parameters looked like or if there was any knock retard.

BigTex, thats exactly what his car does!

two step

The car in Question is mine. The dealer through tech suport with GM think they have solved the problem. Loose ground wire on the left side head.? We will see when I pick her up.

Addendum

Big Tex my car did just as yours at first, but then got progressivly worse. At first it was just the speedo jumping around, nothing worse.
then after time it started to do the surge (when in was realy bad the speedo would show zero mph at 20-50 mph). Oh by the way in only happend under load. 6,5 and forth gear. As it got worse it would even happen at idle.
I'll keep you informed if they fixed it!

BigTex

iTrader: (16)

Please do keep me informed. I have been beginning to wonder if I need to run some top engine cleaner through it or something. Also wonder if it would help to check the plugs. I have TR6s that were used for a few monts with a supercharger and now with nitrous.

I don't have any problems with the speedo. I watched it today via autotap - when it started happening, I tried to keep it happening. After 5 seconds or so, I started seeing some KR and then the timing started going down even more. Funny thing is, it would show 10* with 4 KR and then jiump to 25* and still have 4 KR (or close). Before the KR, timing was in the 12 - 30 range.

two step

Ok Big Tex just receved my car back today from the dealer> everything seems ok! G.M. tech center was overlooking my severice history and noticed that in 2000 my left side cylinder head was removed (bent push rods same dealer seviced it). With that in mind they directed the tech to see if the ground wire on that cylinder head was loose. It was 2 to 3 turns loose! So far so good.

So all I can recomend is that you check your ground wires.

Best luck.
Mike

Big Mike

iTrader: (4)

There ya go! Something as simple (stupid) as a ground wire causing all that havoc. BigTex, let us know how you make out in you situation.

BigTex

iTrader: (16)

Hmmmm. Ground wire? I will check it out. Given that this was the problem, what could you have looked at via Autotap to see what was happening?

When mine happens, I watch: misfires - none, KR - sometimes it is there sometimes not, timing - up and down, MAF - values stay in the same range, MAP - from 96 to 98

I removed some timing w/ LS1 edit in the lower RPMs, and it isn't as bad (it is still there). I also have it set for the converter to unlock easier, so it isn't under the same load.

Will check the ground wires. And give you a reply.

Thanks
Richard